Virtually all of the studies keep agreeing:

Treating cannabis intoxication as if it works the same way as alcohol intoxication creates laws punishing many people for NOT being intoxicated.

"Researchers at the Toronto-based Centre for Addiction and Mental Health gave participants 10 minutes to smoke cannabis to a level they chose, then tested them in a driving simulator.

Because they were allowed to control their own consumption, THC blood levels in the group varied. They ranged from zero to 42 nanograms per mm, which would be nearly 10 times the legal limit to drive [in Canada].

The driving simulator’s scenario involved a nine-kilometre [5.6 mi] drive on a stretch of rural highway signed at 80 km/h [50 mph], with a few simple problems to solve, such as a slow-moving vehicle.

Immediately after smoking, the THC group showed signs of impairment, centering the imaginary car poorly in its lane and driving inappropriately slowly.

But in further tests 24 and 48 hours later, they still had detectable levels of THC, but performed normally in the driving simulator.

'We found significant evidence of difference in driver behaviour, heart rate and self-reported drug effects 30 minutes after smoking cannabis, but … we found little evidence to support residual effects,' the authors wrote.

The study shows that similarly to alcohol, cannabis impairment disappears within a day of consumption at most, if not much earlier.

However, THC can keep showing up on tests long after any impairment has ended — unlike alcohol, which would stop being detectable as impairment went away."

As we've noted many times, appropriate and accurate detection of impairment is not a simple problem to solve at a practical level, but convicting people of crimes they haven't committed because they were not actually intoxicated is a serious issue that absolutely needs to be addressed.


Cannabis and driving study casts doubt on zero-tolerance limits for THC

Do zero-tolerance cannabis limits — for young drivers and police officers, for example — make sense? A new study raises doubts.